1. Field of the Invention
This invention relates generally to doctor systems used to scrape the rotating rolls of papermachines, coaters, and web converting machines and the like for cleaning or dewatering purposes, and is concerned in particular with the provision of a fluid assisted doctor for such doctoring systems.
2. Description of the Prior Art
The three main components of a doctor system include a rigid doctor structure or beam, a doctor blade holder, and a doctor blade. The doctor system is adapted to be mounted in a papermachine, coater or web converting machine and is used to scrape the rotating rolls for cleaning or dewatering purposes. At some critical roll positions in a papermachine, the doctor system is also used during the threading process to remove or "shed" either a full width sheet of paper or a narrower "tail".
In conventional doctoring, the working edge of the doctor blade is loaded against the surface of the rotating roll to provide the scraping or cleaning action. The loading force must be sufficient to hold the blade firmly against the roll surface.
In some cases, the rolls have grooves machined into their surfaces. This makes sheet shedding or cleaning of the roll surfaces with a single doctor difficult, if not impossible. Attempts to address this problem include increasing blade loading forces, which produces other attendant drawbacks, including increased frictional wear of the roll surfaces and doctor blades.